Economic Implications of Selection of Long-Life versus Conventional Caltrans Rehabilitation Strategies for High-Volume Highways
This report presents the results of a two-part study that compared the lifecycle costs of two long-life pavement (LLP) rehabilitation options and several conventional rehabilitation strategies for existing asphalt and concrete pavements, considering both agency costs and road user cost associated with traffic delay caused by construction. In the first part of the research, data from a 1996 study was reanalyzed using a more appropriate method of calculating traffic demand whilst using other assumptions of the earlier study. Then, a factorial sensitivity study was performed comparing lifecycle costs of hypothetical long-life strategies and conventional rehabilitation strategies, but with more variables than were included in the 1996 study and more appropriate data sourced from recent projects. The RealCost software package, developed by the Federal Highway Administration, was used for all analyses.
The results of the analyses showed that for the current data and assumptions (pavement lives, construction productivity, hourly traffic patterns) used in the study together with better traffic delay analysis, the LLP options have greater total costs than conventional rehabilitation alternatives assuming 24-hour-per-day closures for LLP options and 8-hour nighttime closures for conventional alternatives. However, the sensitivity analyses showed that as traffic demand is reduced by implementation of Traffic Management Plans (TMP) and use of weekend closures, the traffic delay costs associated with LLP options are significantly reduced. The sensitivity analyses also showed that if non-pavement costs are reduced for the LLP options (they were not considered for the conventional rehabilitation alternatives), LLP options become competitive for projects with large numbers of lanes.
Because of a lack of good pavement performance data, and limited cost data for long-life projects (two projects), the results of the sensitivity analyses presented in this report should be considered in terms of their general trends, and should absolutely not be used to compare different conventional rehabilitation strategies or alternative long life strategies for individual projects without using better and site-specific data. The alternatives considered in this study are all hypothetical cases. The study was limited to rehabilitation strategies only and is not applicable to new construction or widening.
The sensitivity analyses made clear the need to perform lifecycle cost analysis for each project using project-specific data for both agency costs and road user costs. Despite the findings of this study, LLP is still considered to be a feasible rehabilitation option. It is thus strongly recommended that LCCA be performed on a case-by-case basis when determining whether to use long-life or conventional strategies as significantly different results could be obtained when project specific data and actual overhead and administration costs are used. An example is provided in the report in which lifecycle cost analyses showed LLP to be more cost-effective than conventional rehabilitation alternatives because the existing pavement condition made some conventional rehabilitation alternatives infeasible, which would have resulted in shorter lives than those assumed in this study. Local conditions resulted in a traffic management plan with significantly greater reduction in traffic demand that that assumed in this study.
The results of LCCA are dependent on the following variables which are different for each project:
* Traffic demand patterns, including hourly demand, weekday and weekend demand, directional peaks and discretionary versus job-related travel * Alternative routes and modes * Lane and shoulder configurations and highway geometry in each direction * Feasibility and expected life of each rehabilitation strategy, which depend on truck traffic and existing pavement condition in each lane * Expected construction durations
Sensitivity analyses should be carried out to identify specific issues that influence the agency and road user costs and which could be managed better to reduce the costs on alternative strategies. There is consensus in the industry that quality LCCA in the design phase of rehabilitation projects can result in more appropriate strategies, considerable total savings (agency and road user) and better cash flow management.